1. Field of the Invention
The present invention relates to rack-mount server systems, and more particularly to electronic communication between system components in rack-mount server systems.
2. Description of the Related Art
A rack-mount server system is a powerful, expandable, and customizable computer system in which multiple servers and other computing hardware are consolidated in a rack enclosure. Rack-mount server systems having one or more server racks are typically assembled in a controlled-environment “data center” for servicing the needs of a large organization, such as a company or an online web service. A blade server is one type of rack-mountable server that omits components such as a power supplies, cooling fans, and network switches to achieve a more compact form factor than other rack-mount servers. Multiple blade servers instead share system resources such as power, cooling and network connectivity provided by support modules in the blade server chassis. The compact form factor of a blade server results in an especially high-density system.
A management module is typically provided in the blade server chassis to manage the blade servers. “Management traffic” includes the electronic signals generated by and flowing between the management module and the servers, by which the management module controls the servers and the servers communicate information to the management module. In most systems, the management module communicates with the blade servers over a serial bus network, using communication protocols known in the art such as RS-485, RS232, I2C, SPI, and CAN. Though a point-to-point RS-485 communication link is capable of supporting relatively high-bandwidth management traffic on the order of 10 mbps or more, the actual bandwidth allocated for communication of management traffic over the RS-485 serial bus between the management module and each of the blade servers is typically constrained. For example, signal flow between any two nodes along the RS-485 bus may be electrically limited to a speed on the order of, for example, 250 kbps (kilobytes per second) due to the numerous loads the shared RS-485 bus is required to simultaneously support. This signal flow may be further limited to an effective speed as low as, for example, 1 kbps, due to additional communication protocols that may be implemented, such as for error checking, collision detection, and so forth.
The constrained bandwidth available for communicating management traffic over an RS-485 serial bus network is suitable for certain types of management traffic, such as power on/off, reset, and monitoring of environmental parameters. However, computing technology has evolved to include increasingly high-bandwidth electronic signals, and higher-bandwidth management traffic such as flash updates and video are generally not practical on existing RS-485 serial buses. For example, flash devices rated between 8 MB to 256 MB would require between about 0.5 to 17 minutes or more to flash update at a speeds of 250 kbps. One approach to overcoming this limitation has been to piggyback some of the management traffic across a higher-bandwidth Ethernet connection. However, this solution requires an Ethernet switch to be installed and functional.